1. Field of the Invention
The present invention relates to a tilt type steering column for a motor vehicle. Especially, the present invention relates to a shock-absorbing mechanism of the tilt type steering column.
2. Description of the Related Art
A tilt type steering column allows a steering wheel to move upward and downward so as to secure a proper driving position (attitude) of a seat occupant. The tilt type steering column can have the following construction:
A distance bracket is fixed to the tilt type steering column. A tilt bolt is inserted into the distance bracket. A support bracket otherwise referred to as xe2x80x9cupper clampxe2x80x9d or xe2x80x9cupper bracketxe2x80x9d is fixed to a vehicular body. The tilt bolt has a first end and a second end which engage respectively with a first elongate hole {formed upward and downward in a first side wall of the support bracket} and a second elongate hole {formed upward and downward in a second side wall of the support bracket}. Thereby, the tilt bolt can slidably move upward and upward, or can be fixed in a predetermined position for tilt adjustment.
For securing the seat occupant""s safety in an accident (collision) of the motor vehicle, the shock-absorbing mechanism of the tilt type steering column can have the following functions:
The tilt type steering column can absorb a shock energy which may be caused in a primary collision (namely, a collision of the vehicular body with another vehicular body, an obstacle and the like), and a secondary collision (namely, a collision of the seat occupant with the tilt type steering wheel) attributable to the primary collision, thereby reducing as much as possible or absorbing a load applied to the seat occupant.
The shock-absorbing tilt type steering column has various constructions. As is seen in FIG. 7, Japanese Patent Unexamined Publication No. Heisei 8 (1996)-295251 (=JP8295251) discloses a shock-absorbing tilt type steering column. A steering shaft 19 is rotatably supported by a bearing 20 of a column jacket 21. A support bracket 22 is formed with a vehicular body mounting section 23. The column jacket 21 has a rear end side which is secured to the vehicular body by way of the vehicular body mounting section 23. A distance bracket 24 coupling with the column jacket 21 is formed with an engagement groove 25 opening rearward.
The tilt bolt 26 engages with the engagement groove 25 in such a manner that the tilt bolt 26 can disengage from the engagement groove 25 when an excessive load {greater than an allowable load (upper limit)} is applied to the distance bracket 24. The support bracket 22 has a side wall 27 which is formed with an elongate hole 28. The tilt bolt 26 engages with the elongate hole 28, thus allowing the distance bracket 24 to slide upward and downward. Moreover, operating a tilt lever 29 allows the support bracket 22 to tighten and/or relax the distance bracket 24.
Herein, the shock-absorbing mechanism has the following construction:
An energy absorber 30 has a rear end (right in FIG. 7) formed with a fixture end 31 which couples with the distance bracket 24 through a welding and the like. The fixture end 31 is shaped substantially into a key. The rear end of the energy absorber 30 also has a bent section 32 which is so shaped substantially into an English alphabet xe2x80x9cUxe2x80x9d as to wind about the tilt bolt 26. The energy absorber 30 made of metal is a strap having a predetermined length, and extends forward (leftward in FIG. 7) along the column jacket 21.
In the secondary collision, the above shock-absorbing mechanism can bring about the following effects:
The excessive load {greater than the allowable load (upper limit)} applied axially from the steering shaft 19 to the column jacket 21 by way of the bearing 20 causes the distance bracket 24 to disengage from the tilt bolt 26. Thereby, the tilt bolt 26 which keeps engagement with the support bracket 22 causes plastic deformation to the energy absorber 30, thus absorbing the shock.
With the shock-absorbing tilt type steering column according to the Japanese Patent Unexamined Publication No. Heisei 8 (1996)-295251 (=JP8295251), however, the side wall 27 of the support bracket 22 is in need of a certain dimension for allowing the elongate hole 28 (opening in the side wall 27) to secure a predetermined space for tilting the steering column. Thereby, the side wall 27 dangling downward from the vehicular body mounting section 23 of the support bracket 22 becomes greater than the elongate hole 28 in overall dimension. As a result, a lower section of the support bracket 22 may touch the seat occupant""s knee or thigh, thus discomforting the seat occupant.
Moreover, the energy absorber 30 is partly exposed below the support bracket 22. The energy absorber 30 plastically deformed in the secondary collision may also touch the seat occupant""s knee or thigh. For preventing the energy absorber 30 from touching the seat occupant""s knee or thigh, a cover and the like is supposed to add to the lowermost position of the support bracket 22, resulting in further diminished space above the seat occupant""s knee or thigh.
It is an object of the present invention to provide a shock-absorbing tilt type steering column for a motor vehicle.
It is another object of the present invention to allow the shock-absorbing tilt type steering column to have safe and sufficient space above the seat occupant""s knee or thigh.
According to a first aspect of the present invention, there is provided a shock-absorbing tilt type steering column, comprising:
1) a column jacket having a lowermost section, a space being defined above the column jacket;
2) a coupler;
3) an upper clamp including a pair of a first side wall and a second side wall formed respectively with a first hole and a second hole for tilting the shock-absorbing tilt type steering column, the coupler being inserted into the first hole and the second hole, the space defined above the column jacket being defined in the upper clamp, each of the pair of the first side wall and the second side wall having such a height that a lower end thereof is disposed substantially on a level with or higher than the lowermost section of the column jacket when the coupler is disposed in an uppermost position of each of the first hole and the second hole;
4) a distance bracket sandwiched between the first side wall and the second side wall of the upper clamp in such a manner as to move upward and downward, the distance bracket coupling with the column jacket, the distance bracket being adapted to engage with the coupler in such a manner as to be disengageable from the coupler in a forward direction of a vehicle when a load greater than an upper limit is applied to the distance bracket axially in a direction along the column jacket, the distance bracket being disposed in the space with the lower end of each of the first side wall and the second side wall disposed substantially on the level with or higher than the lowermost section of the column jacket; and
5) an energy absorber interposed between the distance bracket and the coupler.
According to a second aspect of the present invention, there is provided a shock-absorbing steering system, comprising:
1) a column jacket shaped substantially into a cylinder having a lowermost section, the column jacket defining a center section and a front end side, a space being defined above the column jacket;
2) a coupler;
3) an upper clamp disposed in the center section of the column jacket, the upper clamp including a pair of a first side wall and a second side wall formed respectively with a first hole and a second hole, the coupler being inserted into the first hole and the second hole, the space defined above the column jacket being defined in the upper clamp, each of the pair of the first side wall and the second side wall having such a height that a lower end thereof is disposed substantially on a level with or higher than the lowermost section of the column jacket when the coupler is disposed in an uppermost position of each of the first hole and the second hole;
4) a distance bracket sandwiched between the first side wall and the second side wall of the upper clamp in such a manner as to move upward and downward, the distance bracket coupling with the column jacket, the distance bracket being adapted to engage with the coupler in such a manner as to be disengageable from the coupler in a forward direction of a vehicle when a load greater than an upper limit is applied to the distance bracket axially in a direction along the column jacket, the distance bracket being disposed in the space with the lower end of each of the first side wall and the second side wall disposed substantially on the level with or higher than the lowermost section of the column jacket;
5) an energy absorber interposed between the distance bracket and the coupler; and
6) a lower clamp disposed on the front end side of the column jacket.
The other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.